//-----------------------------------------------------------------------------
// GraphicsDeviceControl.cs
//
// Microsoft XNA Community Game Platform
// Copyright (C) Microsoft Corporation. All rights reserved.
//-----------------------------------------------------------------------------

using System;
using System.Drawing;
using System.Windows.Forms;
using Microsoft.Xna.Framework.Graphics;

namespace Xna3DViewer
{
    // System.Drawing and the XNA Framework both define Color and Rectangle
    // types. To avoid conflicts, we specify exactly which ones to use.
    using Color = System.Drawing.Color;
    using Rectangle = Microsoft.Xna.Framework.Rectangle;

    /// <summary>
    /// Custom control uses the XNA Framework GraphicsDevice to render onto
    /// a Windows Form. Derived classes can override the Initialize and Draw
    /// methods to add their own drawing code.
    /// </summary>
    public class GraphicsDeviceControl : Control
    {
        // However many GraphicsDeviceControl instances you have, they all share
        // the same underlying GraphicsDevice, managed by this helper service.
        GraphicsDeviceService graphicsDeviceService;

        /// <summary>
        /// Gets a GraphicsDevice that can be used to draw onto this control.
        /// </summary>
        public GraphicsDevice GraphicsDevice
        {
            get { return graphicsDeviceService.GraphicsDevice; }
        }

        /// <summary>
        /// Gets an IServiceProvider containing our IGraphicsDeviceService.
        /// This can be used with components such as the ContentManager,
        /// which use this service to look up the GraphicsDevice.
        /// </summary>
        public ServiceContainer Services
        {
            get { return services; }
        }

        ServiceContainer services = new ServiceContainer( );

        /// <summary>
        /// Initializes the control.
        /// </summary>
        protected override void OnCreateControl( )
        {
            // Don't initialize the graphics device if we are running in the designer.
            if ( !DesignMode )
            {
                graphicsDeviceService = GraphicsDeviceService.AddRef( Handle,
                                                                     ClientSize.Width,
                                                                     ClientSize.Height );

                // Register the service, so components like ContentManager can find it.
                services.AddService<IGraphicsDeviceService>( graphicsDeviceService );

                // Give derived classes a chance to initialize themselves.
                Initialize( );
            }

            base.OnCreateControl( );
        }


        /// <summary>
        /// Disposes the control.
        /// </summary>
        protected override void Dispose( bool disposing )
        {
            if ( graphicsDeviceService != null )
            {
                graphicsDeviceService.Release( disposing );
                graphicsDeviceService = null;
            }

            base.Dispose( disposing );
        }

        /// <summary>
        /// Redraws the control in response to a WinForms paint message.
        /// </summary>
        protected override void OnPaint( PaintEventArgs e )
        {
            string beginDrawError = BeginDraw( );

            if ( string.IsNullOrEmpty( beginDrawError ) )
            {
                // Draw the control using the GraphicsDevice.
                Draw( );
                EndDraw( );
            }
            else
            {
                // If BeginDraw failed, show an error message using System.Drawing.
                PaintUsingSystemDrawing( e.Graphics, beginDrawError );
            }
        }

        /// <summary>
        /// Attempts to begin drawing the control. Returns an error message string
        /// if this was not possible, which can happen if the graphics device is
        /// lost, or if we are running inside the Form designer.
        /// </summary>
        string BeginDraw( )
        {
            // If we have no graphics device, we must be running in the designer.
            if ( graphicsDeviceService == null )
            {
                return Text + "\n\n" + GetType( );
            }

            // Make sure the graphics device is big enough, and is not lost.
            string deviceResetError = HandleDeviceReset( );

            if ( !string.IsNullOrEmpty( deviceResetError ) )
            {
                return deviceResetError;
            }

            // Many GraphicsDeviceControl instances can be sharing the same
            // GraphicsDevice. The device backbuffer will be resized to fit the
            // largest of these controls. But what if we are currently drawing
            // a smaller control? To avoid unwanted stretching, we set the
            // viewport to only use the top left portion of the full backbuffer.
            Viewport viewport = new Viewport( );

            viewport.X = 0;
            viewport.Y = 0;

            viewport.Width  = ClientSize.Width;
            viewport.Height = ClientSize.Height;

            viewport.MinDepth = 0;
            viewport.MaxDepth = 1;

            GraphicsDevice.Viewport = viewport;

            return null;
        }


        /// <summary>
        /// Ends drawing the control. This is called after derived classes
        /// have finished their Draw method, and is responsible for presenting
        /// the finished image onto the screen, using the appropriate WinForms
        /// control handle to make sure it shows up in the right place.
        /// </summary>
        void EndDraw( )
        {
            try
            {
                Rectangle sourceRectangle = new Rectangle( 0, 0, ClientSize.Width,
                                                                ClientSize.Height );

                GraphicsDevice.Present( sourceRectangle, null, this.Handle );
            }
            catch
            {
                // Present might throw if the device became lost while we were
                // drawing. The lost device will be handled by the next BeginDraw,
                // so we just swallow the exception.
            }
        }


        /// <summary>
        /// Helper used by BeginDraw. This checks the graphics device status,
        /// making sure it is big enough for drawing the current control, and
        /// that the device is not lost. Returns an error string if the device
        /// could not be reset.
        /// </summary>
        string HandleDeviceReset( )
        {
            bool deviceNeedsReset = false;

            switch ( GraphicsDevice.GraphicsDeviceStatus )
            {
                case GraphicsDeviceStatus.Lost:
                    // If the graphics device is lost, we cannot use it at all.
                    return "Graphics device lost";

                case GraphicsDeviceStatus.NotReset:
                    // If device is in the not-reset state, we should try to reset it.
                    deviceNeedsReset = true;
                    break;

                default:
                    // If the device state is ok, check whether it is big enough.
                    PresentationParameters pp = GraphicsDevice.PresentationParameters;

                    deviceNeedsReset = ( ClientSize.Width > pp.BackBufferWidth ) ||
                                       ( ClientSize.Height > pp.BackBufferHeight );
                    break;
            }

            // Do we need to reset the device?
            if ( deviceNeedsReset )
            {
                try
                {
                    graphicsDeviceService.ResetDevice( ClientSize.Width,
                                                      ClientSize.Height );
                }
                catch ( Exception e )
                {
                    return "Graphics device reset failed\n\n" + e;
                }
            }

            return null;
        }


        /// <summary>
        /// If we do not have a valid graphics device (for instance if the device
        /// is lost, or if we are running inside the Form designer), we must use
        /// regular System.Drawing method to display a status message.
        /// </summary>
        protected virtual void PaintUsingSystemDrawing( Graphics graphics, string text )
        {
            graphics.Clear( Color.CornflowerBlue );

            using ( Brush brush = new SolidBrush( Color.Black ) )
            {
                using ( StringFormat format = new StringFormat( ) )
                {
                    format.Alignment = StringAlignment.Center;
                    format.LineAlignment = StringAlignment.Center;

                    graphics.DrawString( text, Font, brush, ClientRectangle, format );
                }
            }
        }

        /// <summary>
        /// Ignores WinForms paint-background messages. The default implementation
        /// would clear the control to the current background color, causing
        /// flickering when our OnPaint implementation then immediately draws some
        /// other color over the top using the XNA Framework GraphicsDevice.
        /// </summary>
        protected override void OnPaintBackground( PaintEventArgs pevent )
        {
        }

        /// <summary>
        /// Derived classes override this to initialize their drawing code.
        /// </summary>
        protected virtual void Initialize( )
        {
        }

        /// <summary>
        /// Derived classes override this to draw themselves using the GraphicsDevice.
        /// </summary>
        protected virtual void Draw( )
        {
        }
    }
}
